Carbene complexes derived from lithiated heterocycles, mainly azoles, by transmetallation

Heterocyclic carbene complex formation can be achieved by lithiation of CH-acidic azoles, transmetallation involving a variety of transition metal complexes and, finally, protonation or alkylation. This article describes the synthetic methodology involved with a special emphasis on unexpected or (presently) unusual features of the reactions or products. The procedure can be extended to allow carbene complex formation by reaction at remote heteroatoms and also for diorgano(carbene) complex formation. Certain azolyls do not substitute but add to coordinated carbonyls and the resulting anionic Fischer-type carbene complexes can function as bidentate ligands. With gold(I) as central metal, many azolyls as well as carbene complexes participate in homoleptic rearrangement. (C) 2001 Elsevier Science B.V. All rights reserved.